Transmission Power Control (TPC) in a mobile communication system is performed in order to attain a reduction of interference in one's own cell and another cell together with a reduction of battery consumption of a terminal device, that is, to attain maintenance of the quality of communication together with a reduction of transmission power. As examples of Transmission Power Control, Open Loop Transmission Power Control that determines the initial transmission power obtained immediately after transmission is started, Closed Loop Transmission Power Control that changes the power in accordance with a change in the propagation environment thereof while communication is being performed, and Outer Loop Transmission Power Control that monitors the quality of communication to make a power control threshold value used in closed loop transmission variable are given.
In Closed Loop Transmission Power Control, the power is varied in units of frames for a certain radio duration. In the front of and in the rear of a boundary between one frame and an adjacent frame where a difference in power is generated, transient-responsive influence is observed. Thus, in Closed Loop Transmission Power Control, a method of setting a duration (hereinafter, referred to as a transition duration), which does not involve data transmission at a head part or a terminal part of a frame, is used. Incidentally, in many systems, setting of a transition duration is determined not only depending on the transient-responsive influence but also depending on composite factors such as a Multi-Path model (for example, a Delay Path length and the number of paths) used and the influence on radio characteristics and data transmission efficiency. (For example, see Japanese Laid-Open Patent Publication No. 2003-324385 and Japanese Laid-Open Patent Publication No. 2003-324382).
In general, a mobile station device used in mobile communication is of a battery-driven type and hence it is desirable for the mobile station device to reduce power consumption. It is also desirable for the mobile station device to be configured to cope with high transmission power in order to maintain the quality of communication. Thus, in many cases, the dynamic range of the transmission power is set higher than 60 to 70 dB. The behavior of transient response observed when the transmission power is increased starting from a state in which the transmission power of a mobile station device is low or is reduced to zero is different from that observed when the transmission power is increased or changed starting from a state in which a certain measure of the transmission power is being transmitted. The influence may be greater exerted on a response waveform and spectrum when the transmission power is increased starting from a state in which the transmission power is low or is reduced to zero than when the transmission power is increased or changed starting from a state that the transmission power is high.
In conventional Transmission Power Control, in some cases, a change in response due to a difference in transmission power is not taken into consideration and hence, in these cases, the radio characteristics are adversely affected by fluctuations of the transmission power. When a change in response due to the difference in transmission power has been taken into consideration, since the transition duration of a radio frame has been conventionally fixed, such processing is performed so that the transition duration is made slightly longer than needed. However, such elongation may be disadvantageous from the viewpoint of data transmission efficiency.